linux-kernel - Re: [RFC 0/3] Introduce per-task latency

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Message-Id: <5c5b61fa-e8f7-5aa7-0fe0-91cb0d4736fb@linux.ibm.com>
Date:   Thu, 5 Dec 2019 22:43:44 +0530
From:   Parth Shah <parth@...ux.ibm.com>
To:     Dietmar Eggemann <dietmar.eggemann@....com>,
        Valentin Schneider <valentin.schneider@....com>,
        linux-kernel@...r.kernel.org
Cc:     peterz@...radead.org, mingo@...hat.com, vincent.guittot@...aro.org,
        patrick.bellasi@...bug.net, qais.yousef@....com, pavel@....cz,
        dhaval.giani@...cle.com, qperret@...rret.net,
        David.Laight@...LAB.COM, morten.rasmussen@....com, pjt@...gle.com,
        tj@...nel.org, viresh.kumar@...aro.org, rafael.j.wysocki@...el.com,
        daniel.lezcano@...aro.org
Subject: Re: [RFC 0/3] Introduce per-task latency_tolerance for scheduler
 hints



On 12/5/19 7:33 PM, Dietmar Eggemann wrote:
> On 05/12/2019 11:49, Valentin Schneider wrote:
>>  
>> On 05/12/2019 09:24, Dietmar Eggemann wrote:
>>> On 25/11/2019 10:46, Parth Shah wrote:
>>>> This patch series is based on the discussion started as the "Usecases for
>>>> the per-task latency-nice attribute"[1]
>>>>
>>>> This patch series introduces a new per-task attribute latency_tolerance to
>>>> provide the scheduler hints about the latency requirements of the task.
>>>
>>> I forgot but is there a chance to have this as a per-taskgroup attribute
>>> as well?
>>>
>>
>> Peter argued we should go for task attributes first, and then
>> cgroup/taskgroups later on:
>>
>> https://lore.kernel.org/lkml/20190905083127.GA2332@hirez.programming.kicks-ass.net/
> 
> OK, I went through this thread again. So Google or we have to provide
> the missing per-taskgroup API via cpu controller's attributes (like for
> uclamp) for the EAS usecase.

I suppose many others (including myself) will also be interested in having
per-taskgroup attribute via CPU controller.

> 
> After reading:
> 
> https://lore.kernel.org/r/20190905114030.GL2349@hirez.programming.kicks-ass.net
> 
> IMHO the following mapping of the existing Android (binary)
> latency_sensitive per-taskgroup flag makes sense:
> 
> latency_sensitive=1 -> latency_tolerance*[-20 .. -1] (less tolerant,
> more sensitive)
> 
> latency_sensitive=0 -> latency_tolerance[0 .. 19] (more tolerant, less
> sensitive)
> 
> Default value is 0 so not latency_sensitive.
> 
> * Since we use [-20 .. 19] as values for latency_tolerance we could name
> it latency_nice. It's shorter ... ?

I kept choosing appropriate name and possible values for this new attribute
in the separate thread. https://lkml.org/lkml/2019/9/30/215
>From which discussion, looking at Patrick's comment
https://lkml.org/lkml/2019/9/18/678 I thought of picking latency_tolerance
as the appropriate name.
Still will be happy to change as per the community needs.

Thanks,
parth